Prostaglandin E(2) in a TLR3- and 7/8-agonist-based DC maturation cocktail generates mature, cytokine-producing, migratory DCs but impairs antigen cross-presentation to CD8(+) T cells

Mature dendritic cells (DCs) represent cellular adjuvants for optimal antigen presentation in cancer vaccines. Recently, a combination of prostaglandin E(2) (PGE(2)) with Toll-like receptor agonists (TLR-P) was proposed as a new standard to generate superior cytokine-producing DCs with high migratory capacity. Here, we compare TLR-P DCs with conventional DCs matured only with the proinflammatory cytokines TNFα and IL-1ß (CDCs), focussing on the interaction of resulting DCs with CD8(+) T-cells. TLR-P matured DCs showed elevated expression of activation markers such as CD80 and CD83 compared to CDCs, together with a significantly higher migration capacity. Secretion of IL-6, IL-8, IL-10, and IL-12 was highest after 16 h in TLR-P DCs, and only TLR-P DCs secreted active IL-12p70. TLR-P DCs as well as CDCs successfully primed multifunctional CD8(+) T-cells from naïve precursors specific for the peptide antigens Melan-A, NLGN4X, and PTP with comparable priming efficacy and T-cell receptor avidity. CD8(+) T-cells primed by TLR-P DCs showed significantly elevated expression of the integrin VLA-4 and a trend for higher T-cell numbers after expansion. In contrast, TLR-P DCs displayed a substantially reduced capability to cross-present CMVpp65 protein antigen to pp65-specific T cells, an effect that was dose-dependent on PGE(2) during DC maturation and reproducible with several responder T-cell lines. In conclusion, TLR-P matured DCs might be optimal presenters of antigens not requiring processing such as short peptides. However, PGE(2) seems less favorable for maturation of DCs intended to process and cross-present more complex vaccine antigens such as lysates, proteins or long peptides

25.1 High Efficiency Monolithic Perovskite Silicon Tandem Solar Cell with a High Bandgap Perovskite Absorber

Monolithic perovskite silicon tandem solar cells can overcome the theoretical efficiency limit of silicon solar cells. This requires an optimum bandgap, high quantum efficiency, and high stability of the perovskite. Herein, a silicon heterojunction bottom cell is combined with a perovskite top cell, with an optimum bandgap of 1.68 amp; 8201;eV in planar p i n tandem configuration. A methylammonium free FA0.75Cs0.25Pb I0.8Br0.2 3 perovskite with high Cs content is investigated for improved stability. A 10 molarity increase to 1.1 amp; 8201;m of the perovskite precursor solution results in amp; 8776;75 amp; 8201;nm thicker absorber layers and 0.7 amp; 8201;mA amp; 8201;cm amp; 8722;2 higher short circuit current density. With the optimized absorber, tandem devices reach a high fill factor of 80 and up to 25.1 certified efficiency. The unencapsulated tandem device shows an efficiency improvement of 2.3 absolute over 5 amp; 8201;months, showing the robustness of the absorber against degradation. Moreover, a photoluminescence quantum yield analysis reveals that with adapted charge transport materials and surface passivation, along with improved antireflection measures, the high bandgap perovskite absorber has the potential for 30 tandem efficiency in the near futur

Tailoring perovskite crystallization and interfacial passivation in efficient, fully textured perovskite silicon tandem solar cells

Fully textured perovskite silicon tandem solar cells are promising for future low-cost photovoltaic deployment. However, the fill factor and open-circuit voltage of these devices are currently limited by the high density of defects at grain boundaries and at interfaces with charge transport layers. To address this, we devise a strategy to simultaneously enhance perovskite crystallization and passivate the perovskite/C60 interface. By incorporating urea (CO(NH2)2) as an additive in the solution step of the hybrid evaporation/spin-coating perovskite deposition method, the crystallization kinetics are accelerated, leading to the formation of the desired photoactive phase at room temperature. With that, perovskite films with large grain sizes (>1 μm) and improved optoelectronic quality are formed at low annealing temperatures (100°C). Concurrently, remnant urea molecules are expelled at the perovskite surface, which locally displaces the C60 layer, thus reducing interfacial non-radiative recombination losses. With this strategy, the resulting tandem solar cells achieve 30.0% power conversion efficiency

The 2020 photovoltaic technologies roadmap

Over the past decade, the global cumulative installed photovoltaic (PV) capacity has grown exponentially, reaching 591 GW in 2019. Rapid progress was driven in large part by improvements in solar cell and module efficiencies, reduction in manufacturing costs and the realization of levelized costs of electricity that are now generally less than other energy sources and approaching similar costs with storage included. Given this success, it is a particularly fitting time to assess the state of the photovoltaics field and the technology milestones that must be achieved to maximize future impact and forward momentum. This roadmap outlines the critical areas of development in all of the major PV conversion technologies, advances needed to enable terawatt-scale PV installation, and cross-cutting topics on reliability, characterization, and applications. Each perspective provides a status update, summarizes the limiting immediate and long-term technical challenges and highlights breakthroughs that are needed to address them. In total, this roadmap is intended to guide researchers, funding agencies and industry in identifying the areas of development that will have the most impact on PV technology in the upcoming years

High-temperature contact formation on n-type silicon: Basic reactions and contact model for seed-layer contacts

Contact formation on n-type silicon, especially using a high-temperature process, has been the subject of research for more than 40 years. After its application in microelectronics, n-type silicon is widely used in silicon solar cells as the emitter layer. The formation of a low ohmic contact grid using an industrially feasible process step is one of the key features required to improve the solar-cell efficiency. The contact materials, typically deposited in a printing step, have to fulfil several functions: opening the dielectric antireflection layer and forming an intimate metal-semiconductor contact with good mechanical adhesion and low specific contact resistance. As the used contact inks typically contain several functional materials, such as silver and a glass frit, the detailed contact formation is still not entirely understood. Therefore, the chemical reactions during the contact firing process have been studied in detail by thermogravimetric differential thermal analysis in combination with mass spectroscopy. Based on these studies, a contact ink has been developed, optimized and tested on silicon solar cells. In this paper, the mechanism of the etching process, the opening of a dielectric layer, the influence of different atmospheres and the impact of the glass-frit content are investigated. The observed microscopic contact structure, the resulting electrical solar-cell parameters and the studied reactions are combined to clarify the physics behind the high-temperature contact formation

Improved parameterization of Auger recombination in silicon

Accurate modeling of the intrinsic recombination in silicon is important for device simulation as well as for interpreting measured effective carrier lifetime data. In this contribution we study the injection-dependent effective carrier lifetime applying advanced surface passivation techniques based on Al2O3 or SiNx We show that in some cases the measured lifetime data significantly exceeds the previously accepted intrinsic lifetime limit proposed by Kerr and Cuevas [1]. To verify our measurements we independently perform lifetime measurements with different measurement techniques in two different laboratories. Based on effective lifetime measurements we develop an advanced parameterization of the intrinsic lifetime in crystalline silicon at 300 K as a function of the doping density and the injection level, which accounts for Coulomb-enhanced Auger recombination and Coulomb-enhanced radiative recombination